Product Details

Modicon PC-E984-381 is a high-performance 984 plc cpu controller and reliable local i/o programmable processor belonging to the Modicon 984-38X family, designed for local I/O control without native Modbus Plus support. This modbus legacy cpu serves as the central control core for small and medium automation racks, compatible with Modicon 800 series local I/O modules, programmed with LL984 ladder logic via Modsoft software. It carries 16K words of user logic memory and 1920 register words, protected by battery-backed RAM to retain programs and process data after power loss. Equipped with dual built-in Modbus communication ports and an integrated time-of-day clock, it supports connection to HMI terminals, operator panels and other Modbus slave devices. It only supports up to two local I/O racks with a maximum of 512 mixed discrete I/O points and 32 analog input plus 32 analog output channels, making it ideal for skid-mounted equipment and standalone process units. The scan speed reaches 3 ms per thousand logic nodes, delivering stable cyclic logic execution. Built with industrial-grade components and conformal coated PCB, it can run continuously under vibration, dust and electrical noise in production plants. As a discontinued legacy spare, this 984 plc cpu controller acts as a drop-in replacement to restore local sequential and closed-loop control for ageing Modicon 984 automation racks.

Basic Parameters

Brand: Modicon (AEG / Schneider legacy)

Model: PC-E984-381

Product Type: 984‑38X Series Local I/O PLC CPU Processor

Compatible Rack: Modicon 984 chassis, 800 series local I/O modules

Programming Software: Modsoft

Logic Language: LL984 Ladder Logic

User Logic Memory: 16K words

Register Memory: 1920 words, battery‑backed

Scan Speed: 3 ms / 1K logic nodes

Communication: Dual Modbus serial ports, no Modbus Plus

Clock: Built‑in time‑of‑day clock

Max Local I/O: 512 discrete I/O, 32AI / 32AO, up to two local racks

Power Input: 115 / 230 VAC, 50 / 60 Hz

Indicator: Front LED for run, fault, Modbus activity and diagnostic status

Mounting: Single‑slot rack installation

Product Status: Discontinued, end of original production

Net Weight: Approximately 1.35 kg

Supported Functions

This 984 plc cpu controller performs cyclic scanning of user ladder logic and all connected local 800‑series I/O modules. The local i/o programmable processor supports timer, counter, arithmetic operation, comparison and PID closed‑loop regulation for temperature, flow, pressure and liquid level control. This modbus legacy cpu exchanges real‑time discrete and analog data through its dual Modbus ports, sending process values to HMI and receiving operator setpoints and start‑stop commands. It supports sequential batch control, alarm management and scheduled logic triggered by the onboard real‑time clock. It runs comprehensive built‑in self‑diagnostics to detect memory failure, communication timeout, backplane bus error and low backup battery voltage. When critical faults are detected, it forces outputs to predefined safe states to protect field actuators and process equipment. It works cooperatively with discrete input, discrete output and analog modules to build a complete local control system.

Core Functions

As the central local‑only programmable processor, this 984 plc cpu controller reads sensor and switch signals, executes user control logic and drives field actuators. Its dual Modbus ports provide flexible serial communication for local supervision, while its fixed local rack architecture simplifies maintenance for legacy skid systems. This modbus legacy cpu works as a direct spare to rebuild stable local automatic control for ageing Modicon 984 automation racks.

Hardware Specifications & Environmental Features

Operating Temperature: 0°C ~ +60°C

Storage Temperature: -20°C ~ +70°C

Relative Humidity: 5%–95%, non‑condensing

Housing: Rugged metal shielded single‑slot module casing

Protection: Hardware watchdog, transient suppression, lithium battery backup circuit

Anti-interference: Isolated Modbus serial ports, low‑noise power conversion

Compatibility: Modicon 800 series I/O, Modbus compatible HMI and slave devices

Industry Applications: Applied in legacy petrochemical distributed control, old paper making production automation, material handling conveyor lines, packaging and textile machinery, water treatment remote signal collection and large conveyor remote I/O control racks.

Note: Confirm program backup, backup battery health, Modbus address settings and compatibility with 800 series local I/O modules before ordering.

This is from our current stock.

available stock.xlsx